Ore flotation collector and ore flotation process



United States Patent 3,073,448 ORE FLOTATION COLLECTOR AND ORE FLOTATION PROCESS Miles R. McCorkle, Oswego, Robert E. Baarson, La Grange, Sidney H. Shapiro, Chicago, and Harold B. Treweek, Park Forest, 111., assignors, by mesne assignments, to Armour and Company, Chicago, 11]., a corporation of Delaware No Drawing. Filed Oct. 28, 1960, Ser. No. 65,603

Claims. (Cl. 209-166) This invention relates to an ore flotation collector which has particular utility in the froth flotation of silica containing phosphate ores, and therefore the invention also relates to a phosphate ore flotation process.

At the present time primary fatty monoamines are widely used in the froth flotation of silica containing phosphate ores. The amine flotation is commonly employed for the final concentration of the phosphate rock, the coarse silica having been separated in an earlier flotation stage. The amines are ordinarily used in their salt form, such as the acetate salt. The amine collector, being strong. 1y cationic, causes the silica to float and it is removed in the froth or overflow. The desired product, being the concentrated phosphate rock, is removed in the underflow. The phosphate concentrate thus produced should contain a minimum of silica, preferably not more than 3% or 4% by weight. I

Since amine collectors have become virtually standard reagents in the flotation of phosphate ores, a great deal or research has been directed toward the improvement of such collectors. In evaluating amine collectors two factors are of major importance. These arethe strength of the collector, which is a measure of the quantity of the collector required to obtain a particular degree of separation, and the selectivity of the collector, which is a measure of the amount of the phosphate rock recovered. For example, collector strengths can be evaluated in terms of the pounds of collector required per ton of flotation feed to obtain a particular concentration of acid insolubles (a measure of silica content) in the product. Collectorselectivity can be determined by comparing the percent of phosphate rock recovered with the percent of insolubles in the product. The recovery may be stated in terms of tricalcium phosphate content which is usually designated in the industry as bone phosphate of lime (BPL). As indicated, the siliceous gangue constituents of phosphate rock are commonly determined and reported as acid insolubles (INSOL) A primary object of the present invention is to increase the selectivity and/or strength of primary fatty monoamine ore flotation collectors. Still another object is to provide a means for increasing the selectivity of such collectors Without unduly increasing the collector consumption rate. The way in which these and other objects are achieved will be indicated in the following detailed specification.

The present invention can be practiced by a very simple procedure. The primary fatty monoamines, such as the commercially available primary amine mixtures prepared from tallow fatty acids, soybean fatty acids, cottonseed fatty acids, etc., are heated under oxidizing conditions to convert a portion of the amines to a non-basic form. The resulting product, either as such or blended with other amines, is used as a collector for the concentration of phosphate ore. While it has particular utility for flotation of silica from phosphate, this reagent can also be used to advantage for the beneficiation of other ores containing minerals, such as micas, feldspars, heavy metals, silica, sands, potash, barite, calcite, fluorspar, etc. While the procedure is simple, and the improvement in the collector is evident, no way is known of fully characterizing the improved collector except in terms of the process by which it is prepared, and no theoretical explanation for the improvement can be given.

V The primary fatty monoamines useful in practicing this invention will contain predominately from 12 to 22 carbon atoms. One preferred class of such amines are those containing predominately from.16 to 18 carbon atoms, such as the amines formed from palmitic and stearic acids. With primary amines prepared from the fatty acid mixtures derived from natural oils and fats, there will usually be some minor proportion of amines containing less than 12 carbon atoms but this is not objectionable.

In accordance with the present invention, the primary amines are activated by heating them at a temperature below the flash point while introducing an oxygen-providing gas and bringing the heated amines into intimate contact with the gas. At temperatures below C., unless a catalyst is employed, the reaction proceeds slowly, While at temperatures above 165 C. the reaction is difiicult to control. Preferably a temperature within the range from to 150 C. is employed. For purposes of convenience and economy, ordinary air may be used as the oxygen-providing gas, but oxygen itself may be used, or the oxygen for the reaction may be supplied in some other suitable way.

The reaction may be carried out in an enclosed vessel provided with a heating jacket, a mechanical agitator, a sparger for introducing the air into the body of liquid, and a vent for exhausting air from the top of the vessel after it has passed through the liquid. It is not necessary to conduct the reaction under pressure, since good results are obtained at a pressure of substantially one atmosphere. To provide for the continuous flow of air through the mixture during the reaction, the air will have to be introduced into the vessel under pressure, but the interior of the vessel need only be at a pressure slightly higher than atmospheric to maintain the desired flow. Preferably, the air and heated amines are brought into intimate contact by agitation and mixing.

Where the reaction product is to be used as a collector without blending it with other amines, the desired degree of activation can usually be achieved in less thanrsix hours. At temperatures below 100 C., a longer reaction time may be required, but at the preferred temperatures a substantially shorter reaction time will be suflicient. For.

example, when using temperatures from to C.,' a reaction time of 3 to 4 hours will usually besuflicient.

Although the chemical composition of the final product is not known with certainty, the progress of the reaction can be followed and the extent of reaction controlled by periodically drawing off samples of the reaction mixture.

able to reduce the titratable nitrogen by more than 60%,

and where the product is to be used as produced, it is preferred not to reduce the titratable nitrogen by over 35%. Since the percent of titratable nitrogen is a measure of amine content, it may be inferred that in the course of the reaction monoamines are oxidized and a non-tritratable material is formed therefrom. This is be lieved to be the case, although no way is known of characterizing this non-titratable material by routine analytical methods except in terms of the process of preparing it. It is believed that the reaction is not the conversion of the amines to amides, but something much more subtle and complex. The desired reaction proceeds under sub stantially anhydrous conditions, whereas it is known that the presence of water is required to form amides. Possibly several different compounds may be formed from the reaction described above. These are believed to be some form of oxidized derivatives of the primary amines, but no reaction mechanisms have heretofore been elucidated which would appear to account for the results obtained.

For use as a collector in separating silica from phosphate rock, it is desirable for the collector to contain from 40 to 95% by weight of the primary fatty monoamines in admixture with from 5 to 60% by weight of the nontitratable material produced by the procedure described above. Preferred proportions are from 65 to 85% primary amine and from 15 to 35% of the non-titratable material. Where the reaction has been carried beyond the desired proportions, the reaction product can be blended with additional quantities of the primary amines to achieve the optimum proportions. However, as indicated above, by following the reduction in titratable nitrogen during the course of the reaction, the product can be directly produced containing the primary amines and the activating component in the desired proportions.

The ore flotation collector prepared as described in the foregoing specification can be used in the separation of silica from phosphate rock in the same manner as the primary fatty monoamines would be employed. In other words, all that is necessary is to subject the silica containing phosphate ore to froth flotation in the presence of the improved collector. No new or special operating techniques are required. Since the details of froth flotation as applied to the treatment of phosphate ores are wellknown, it is thought to be unnecessary to repeat them here. In accordance with known procedures, the flotation feed will be deslimed, conditioned with the collector for a brief but finite time at or near flotation pulp density, and subjected to froth flotation in a flotation cell. In the operation of the cell, the silica or tails will be removed with the froth or overhead, and the concentrated phosphate rock will be recovered in the underflow.

It will be understood that the collector in addition to the components previously described may contain a minor proportion of secondary or tertiary amines. Commercial grades of primary amines may contain from 5 to of secondary amines together with smaller percentages of tertiary amines, and some additional secondary and tertiary amines may be formed in the heating procedure described above.

It will also be understood that the amines in the col- 'lector may be employed in their salt form, that is, as amine acetate, amine hydrochloride, etc. In other Words, the titratable amine portion of the collector may be reacted with acetic acid or other acidic reagent to form amine salts before the collector is used in the flotation cell.

The present invention is further illustrated by the following examples, some of which provide more specific directions for practicing the invention, and others are experimental examples showing results which have been obtained.

EXAMPLE 1 2500 grams of primary tallow monoamine were charged into a 5 liter flask and heated to C. while stirring. Air was introduced below the surface of the liquid at the rate of approximately 1.5 liters per minute and the temperature gradually increased to C. over a period of 6.5 hours until the primary amine content dropped from 95.7% to 76.6%, as determined by the standard analytical procedures. The total amine content decreased from 97.4% to 84.3%. Total amine content was determined by titration with alcohol HCl to bromphenol blue end point. Additional samples were treated with salicylaldehyde and phenylisocyanate, respectively, and again titrated to a bromphenol blue end point with alcohol HCl. The data showed that the apparent molecular weight had increased from 269 to 311, and the titratable nitrogen had correspondingly decreased from 0.372 meg/gm. to 0.322 meg/gm.

EXAMPLE 2 A standard flotation testing procedure was employed in the evaluation and comparison of the collectors described in this and the following examples, and all testing was conducted on a sample of deoiled rougher flotation concentrate which was obtained from an industrial phosphate beneficiation operation. This material, referred to in the examples as feed, analyzed 21.1% acid insoluble and 61.1% BPL.

The titratable amine portions of all collectors evaluated and reported herein was fully neutralized with glacial acetic acid, and 5% (by weight) aqueous dispersions of the resultant acetate salts were added to the flotation cell.

For each test, 500 g. (dry basis) of thoroughly deslimed feed was charged to the cell of a Fagergren flotation machine. Prior to feed dilution to flotation density, NaOH equivalent to 0.10 lb. per ton of feed was added to the cell to provide final flotation pH of 7.3-7.6. Following pulp dilution to flotation density 0.10 lb. of Dowfroth 250 frothing agent, amine acetate primary collector, and kerosene auxiliary collector were added to the float cell, and the resultant reagent-pulp mixture was conditioned for A min. For each test, two parts of kerosene were added for each part of the particular amine acetate collector employed. Following conditioning, air was in troduced to the float cell and one silica froth product (tailing) was removed from the cell.

The results of flotation with the acetate salt of the collector prepared as described in Example 1 and containing 76.6% primary tallow amine are presented in Table I to demonstrate the improved flotation selectivity realized by practice of the invention. The results of flotation with the acetate salt of the unmodified tallow amine containing 95.7% primary amine are presented in Table II.

Table l Oxidized Concentrate Tails Armeen Percent Test A B No. lbs/Ton Percent Percent Percent. Percent Percent Recov- Feed Weight Acid BP Weight BPL cry Insol.

Table II Concentrate Tails Armeen Percent Test Ac, BPL No. lbs/Ton Percent Percent Percent Percent Percent Recov- Feed Weight Acid BPL Weight; BPL cry 7 EXAMPLE 3 The cationic collector used in this example was also prepared according to the method of Example 1, except that primary soya monoamines were used. The pretreatment reduced the titratable nitrogen from 0.370 meg./ gm. to 0.283 meg/gm. and the primary soya amine content from 96.8% to 65.8%. The results of flotation with the acetate salt of this reagent are shown in Table III.

While in the foregoing specification this invention has been described in connection with certain specific embodiments thereof and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the ore flotation art that the invention is susceptible to additional embodiments and that many of the details described herein can be varied considerably without departing from the basic principles of the invention.

We claim:

1. An ore flotation collector, comprising primary fatty monoamines containing predominately from 12 to 22 carbon atoms in admixture with an activating component prepared by heating primary fatty monoamines contain ing predominately from 12 to 22 carbon atoms while introducing an oxygen-providing gas into said heated monoamines and bringing said heated monoamines into intimate contact with said gas until the titratable nitrogen is reduced by at least 5%, thereby oxidizing said monoamines and forming a non-titratable material, said flotation collector containing from 40% to 95% by weight of said primary fatty monoamines and from 5 to 60% by weight of the said non-titratable material.

2. The ore flotation collector of claim 1 wherein said collector contains from 65 to 85% by weight of said primary'fatty monoamines and from 15 to 35% by weight of the said non-titratable material.

3. An ore flotation collector prepared by heating primary fatty monoamines containing predominately from 12 to 22 carbon atoms at a temperature from 70 to 165 C. while introducing an oxygen-providing gas into said heated monoamines and bringing said heated monoam-ines into intimate contact with said gas until the titratable nitrogen is reduced by from 10 to 4. The ore flotation collector of claim 3 wherein said titratable nitrogen is reduced by from 15 to 35%.

5. The phosphate ore flotation process characterized by subjecting silica containing phosphate ore to froth flotation in the presence of the collector of claim 1.

6. The process of claim 5 wherein said collector contains from to by weight of said primary fatty monoamines and from 15 to 35% by weight of the said nontitratable material.

7. A phosphate ore flotation process characterized by subjecting silica containing phosphate ore to froth flotation in the presence of the collector of claim 3.

8. A process of claim 7 wherein the titratable nitrogen is reduced by from 15 to 35 9. An ore flotation collector prepared -by heating primary fatty monoamines containing predominately from 16 to 18 carbon atoms at a temperature of from to C. while introducing air into said heated monoamines and bringing said heated monoamines into intimate contact with said air until the titratable nitrogen is reduced by from 15 to 35%.

10. A phosphate ore flotation process characterized by subjecting silica containing phosphate ore to froth flotation in the presence of the collector of claim 9.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES The Chemistry of Fatty Amines by Armour Chemical Division, Armour and Company, 1948, page 13. 

3. AN ORE FLOTATION COLLECTOR PREPARED BY HEATING PRIMARY FATTY MONOAMINES CONTAINING PREDOMINATELY FROM 12 TO 22 CARBON ATOMS AT A TEMPERATURE FROM 70 TO 165* C. WHILE INTRODUCING AN OXYGEN-PROVIDING GAS INTO SAID HEATED MONOAMINES AND BRINGING SAID HEATED MONOAMINES INTO INTIMATE CONTACT WITH SAID GAS UNTIL THE TITRATABLE NITROGEN IS REDUCED BY FROM 10 TO 60%. 